1. Field of the Invention
The present invention relates to a structure for mounting a current detection resistor device suitable for use in current detection circuit and the like in a switching power circuit, and relates in particular to a technique of mounting a low resistance resistor device on a circuit board for detecting a large current containing high frequency components that may cause problems of parasitic inductance.
2. Description of the Related Art
In recent years, with the trend towards the use of CPU chips operating at low voltage and large current in electronic devices such as personal computers, switching power source including DC/DC converter and the like has been used for supplying a power to the circuits. In such a switching power circuit, a current detection resistor device is being used in frequency bands ranging from several tens to several hundreds kilo Herz (kHz). A saw-teeth waveform current flows ranging from several amperes to several tens of amperes to detect the magnitude of current on the basis of a voltage generated at the both ends of the low resistance resistor device. In such a current detection resistor device, it is necessary that the resistance be as low as practical, typically less than several mili-ohms and also it is desirable that the parasitic inductance of the resistor device itself be as low as possible. This is because the resistance value of the resistor device itself is low and the frequency is relatively high, so that even for a small inductance at the level of 1 nH, the combined impedance generated at the both ends of the resistor device becomes high to produce voltage detection error.